People with intellectual and/or developmental disabilities (IDD) living in group homes are more likely to have poor oral hygiene, poor dietary practices, increased decay, periodontal disease, and total tooth loss than the general population-a significant health disparity. To improve the oral health care of this population, we are conducting a stratified cluster Phase 2 randomized controlled trial to test for the efficacy of an oral health promotion (OHPROM) strategy on persons with IDD living in group homes. This intervention is based on behavioral and public health theory derived from the literature and includes features to enhance sustainability. The sample of consented participants is projected to be about 23 home managers, 258 caregivers, and 258 persons with IDD who reside in 86 group homes. Assuming the attrition rate observed in a pilot study, it is projected that the final participants will be 20 managers, 240 caregivers, and 240 persons with IDD residing in 80 group homes. The homes are managed by three nonprofit partnering organizations and three sites of ResCare, the nation's largest provider of residential services to persons with IDD in or near the Metro Louisville area in Kentucky and Southern Indiana. Managers are responsible for the conduct of caregivers in a small cluster of group homes, are generally former caregivers, and are paid staff. Caregivers are responsible for ensuring daily personal hygiene and dietary guidance for persons with IDD and are paid staff of the partner organizations. The OHPROM strategy is comprised of (a) planned action that entails caregivers signing a behavioral contract and engaging in oral health action planning for persons with IDD, (b) caregiver capacity- building that includes didactic and observational learning as well as oral health devices, (c) environmental adaptations with reminder posters and change of oral hygiene location (physical environment) and administrative oral health support (social environment), and (d) reinforcement through caregiver coaching. The primary study objective is to assess change in oral health status of persons with IDD living in group homes. A second objective is to assess change in proximal and intermediate outcomes (i.e., mechanisms of change) and the extent to which these outcomes moderate the intervention effects on the oral health of persons with IDD. As a third objective, the study will assess implementation quality as delivered to home managers and caregivers and the association of intervention components with the mechanisms of change. The study results are intended to affect the fields of dentistry and behavioral research by demonstrating whether a theory-based prevention strategy can improve the oral health of persons with IDD living in group homes and may also improve the oral health of other at-risk dependent populations. Ultimately, the study may produce changes in service organizations, oral health care policies, and practices of the study organizations. Diffusion of the tested oral health strategy, if proven efficacious, is also important; thus, creating infrastructure for diffuson is also a study priority.